Genetic engineering has allowed the improvement of microorganisms used as industrial bioreactors, cell factories and in food fermentations. Gram-positive organisms, including a number of Bacillus species, are used to produce a large number of useful proteins and metabolites (see, e.g., Zukowski, “Production of commercially valuable products,” In: Doi and McGlouglin (eds.) Biology of Bacilli: Applications to Industry, Butterworth-Heinemann, Stoneham. Mass. pp 311-337 [1992]). Common Bacillus species used in industry include B. licheniformis, B. amyloliquefaciens and B. subtilis. Because of their GRAS (generally recognized as safe) status, strains of these Bacillus species are natural candidates for the production of proteins utilized in the food and pharmaceutical industries. Examples of proteins produced in Gram-positive organisms include enzymes, e.g., α-amylases, neutral proteases, and alkaline (or serine) proteases.
In spite of advances in the understanding of production of proteins in bacterial host cells, there remains a need for to develop new recombinant strains that express increased levels of a protein of interest.